Synthesis, reactivity and structural characterization of some heterometallic complexes containing naked arsenic ligands

The reactions of [Co-2(mu-As-2)(CO)(6)] with [Mo2Cp2(CO)(4)] (Cp=eta(5)-C5H 5) and with [(OC)(4)CoMCp(CO)(3)] [M=Mo or W] gave, respectively, the known product [Mo-2(mu-As-2)Cp-2(CO)(4)] 1 and the new heterobimetallic complexe s [(OC)(3)Co(mu-As-2)MCp(CO)(2)] [M=Mo 2 or W 3]. The mixed-metal complexes have been treated with PPh3 to give the substituted complexes [(Ph3P)(OC)( 2)Co(mu-As-2)MCp(CO)(2)] [M=Mo 4 or W 5]. Complex 2 reacted with [Cr(CO)(5) ]. THF to give [(OC)(3)Co{mu-As-2[Cr(CO)(5)](2)}MoCp(CO)(2)] 6. Reaction of [MoWCp2(CO)(4)] with [Co-2(mu-As-2)(CO)(6)] does not lead to the complex [ MoW(mu-As-2)Cp-2(CO)(4)] although this can be obtained by co-thermolysis of [Mo2Cp2(CO)(6)] and [W2Cp2(CO)(6)] with grey arsenic which affords three b imetallic products, [MM'(mu-As-2)Cp-2(CO)(4)] (M=M'=Mo 1; M=Mo, M'=W 7; M=M '=W), and four trimetallic products, [M2M'(mu(3)-As)Cp-3(CO)(6)] (M=M'=Mo; M=Mo, M'=W 8; M=W, M'=Mo 9; M=M'=W). The new heterometallic complexes 2, 3, 5, 6 and 9 have been characterized by X-ray diffraction analyses.